Just realized I never responded here. Short answer: because publishers fix e-book prices, but retailers can set the prices of print books whereve they want. The result is that Random House could price the Kindle Brainiac as low as they wanted...but Amazon or whoever else could always undersell that for reasons of their own.

If you are one convinced that publishing is scared of what e-books represent for their future, there may still be grist for your mill here. For example: if Amazon's current discount on the Brainiac trade paperback isn't unusual...then why did Random House set the e-book price higher than what they knew Amazon would charge for paper?